CN113030238B - Image acquisition system and image acquisition method - Google Patents
Image acquisition system and image acquisition method Download PDFInfo
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Classifications
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- G06V—IMAGE OR VIDEO RECOGNITION OR UNDERSTANDING
- G06V20/00—Scenes; Scene-specific elements
- G06V20/60—Type of objects
- G06V20/69—Microscopic objects, e.g. biological cells or cellular parts
- G06V20/693—Acquisition
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R33/00—Arrangements or instruments for measuring magnetic variables
- G01R33/12—Measuring magnetic properties of articles or specimens of solids or fluids
- G01R33/1292—Measuring domain wall position or domain wall motion
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/72—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating magnetic variables
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N23/00—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00
- G01N23/22—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material
- G01N23/225—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material using electron or ion
- G01N23/2251—Investigating or analysing materials by the use of wave or particle radiation, e.g. X-rays or neutrons, not covered by groups G01N3/00 – G01N17/00, G01N21/00 or G01N22/00 by measuring secondary emission from the material using electron or ion using incident electron beams, e.g. scanning electron microscopy [SEM]
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- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
- G01R33/032—Measuring direction or magnitude of magnetic fields or magnetic flux using magneto-optic devices, e.g. Faraday or Cotton-Mouton effect
- G01R33/0325—Measuring direction or magnitude of magnetic fields or magnetic flux using magneto-optic devices, e.g. Faraday or Cotton-Mouton effect using the Kerr effect
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- G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
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- G01R33/09—Magnetoresistive devices
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Abstract
The present invention relates to an image acquisition system and an image acquisition method. In an image acquisition system, strain distribution is easily measured over a wide range. A reference magnetic domain image of a sample to be a reference is obtained by using a reference external magnetic field to be a reference and irradiating light, a plurality of magnetic domain images are obtained in a state in which the external magnetic field is applied while being changed, a plurality of subtraction images in which the reference magnetic domain image is subtracted from the plurality of magnetic domain images are obtained, a magnetic domain inversion region in which a magnetic domain is inverted is extracted from the plurality of subtraction images, and a plurality of subtraction images each having the magnetic domain inversion region are synthesized to obtain a synthesized image having the plurality of magnetic domain inversion regions.
Description
Technical Field
The present invention relates to an image acquisition system and an image acquisition method.
Background
In recent years, energy saving is demanded for reducing environmental load. With this trend, it is urgent to increase the performance, control, efficiency, and power consumption of electronic control components such as motors, solenoids, and transformers. These components mainly comprise wires and iron cores, which perform the conversion of electric energy and magnetic energy. Here, energy conversion with good energy efficiency is most important in energy saving measures.
The iron core is mainly made of soft magnetic material, and generally made of electromagnetic steel plate. In electromagnetic steel sheets and soft magnetic materials, when stress or strain is generated, the strength and magnetic properties of the materials change. In general, stress and strain cause embrittlement of materials, and the like, and cause breakage. In addition, non-uniformity of magnetic properties within the sample may prevent improvement of properties.
However, in some electromagnetic steel sheets, the performance can be improved by effectively controlling the strain. In the magnetic material, it is known that the magnetic properties vary greatly depending on the shape, size, grain diameter variance, grain boundary shape between particles, and the like of the particles.
Therefore, means are needed to easily determine the presence or absence of strain and evaluate the area affected by the strain, and to further clarify the cause of strain generation. At the same time, means for evaluating the shape, particle diameter variance, and the like of particles are also required.
Conventionally, as a method used for stress strain evaluation, there are a method using X-rays and a method for measuring a change in lattice constant based on a Transmission Electron Microscope (TEM), electron beam back scattering diffraction (EBSD), or the like. In addition, as particle size analysis, there is a method using a reflected electron (BSE) image. For example, patent document 1 discloses a technique for estimating magnetic permeability based on a known material.
Prior art literature
Patent literature
Patent document 1: JP 2002-156361A
In the past, in measurement using X-rays used for stress-strain evaluation, since only the average strain value of the entire sample piece was known, the place where the strain occurred could not be specified. In addition, strain measurement by TEM is an evaluation on the order of nm, and it is difficult to measure a sample in a large scale.
In the same way, since the surface is also required to be smoothed in the strain measurement by EBSD, the sample surface needs to be processed for observation. Therefore, it is difficult to analyze the cause of the strain, and the frequency of the strain and the cause of the strain cannot be clarified.
In addition, in order to perform particle size analysis from a BSE image, the sample needs to be placed in vacuum, which limits the shape of the sample.
According to the method disclosed in patent document 1, although the magnetic permeability can be estimated based on a known material, the strain distribution state cannot be grasped. Therefore, it is desired to easily measure strain distribution over a wide range.
Disclosure of Invention
The purpose of the present invention is to easily measure strain distribution over a wide range in an image acquisition system.
An image acquisition system according to an aspect of the present invention includes a signal processing unit that acquires an image of a sample including a magnetic substance, and the signal processing unit performs: a method for manufacturing a magnetic domain inversion device includes obtaining a reference magnetic domain image of a sample to be a reference by irradiating light using a reference external magnetic field to be a reference, obtaining a plurality of magnetic domain images while applying the external magnetic field while changing the external magnetic field, obtaining a plurality of subtraction images each obtained by subtracting the reference magnetic domain image from the plurality of magnetic domain images, extracting a magnetic domain inversion region having a magnetic domain inversion from the plurality of subtraction images, and obtaining a composite image having a plurality of the magnetic domain inversion regions by combining the plurality of subtraction images each having the magnetic domain inversion region.
An image acquisition method according to an aspect of the present invention is an image acquisition method for acquiring an image of a sample including a magnetic substance, the image acquisition method including: obtaining a reference magnetic domain image of the sample serving as a reference by irradiating light using a reference external magnetic field serving as a reference; acquiring a plurality of magnetic domain images while applying an external magnetic field while changing the external magnetic field; obtaining a plurality of subtraction images respectively subtracting the reference magnetic domain image from the plurality of magnetic domain images; extracting magnetic domain inversion regions of magnetic domain inversion from the plurality of subtracted images, respectively; and obtaining a composite image having a plurality of the magnetic domain inversion regions by compositing a plurality of the subtracted images each having the magnetic domain inversion region.
ADVANTAGEOUS EFFECTS OF INVENTION
According to one aspect of the present invention, in an image acquisition system, strain distribution can be easily measured over a wide range.
Drawings
Fig. 1 is a diagram showing the configuration of an image acquisition system according to embodiment 1.
Fig. 2 is a flowchart showing an image acquisition method according to embodiment 1.
Fig. 3 is an explanatory diagram showing an example of a method of acquiring a subtraction image.
Fig. 4 is an explanatory diagram showing an example of the subtraction image.
Fig. 5 is an explanatory diagram showing an example of the structure of a drawing (mapping) image of a magnetization reversal region.
Fig. 6 is an explanatory diagram showing an example of the structure of the strain distribution diagram.
Fig. 7 is an explanatory diagram showing an example of the operation GUI of embodiment 1.
Fig. 8 is a flowchart showing an image acquisition method according to embodiment 2.
Fig. 9 is a flowchart showing an image acquisition method according to embodiment 3.
Fig. 10 is an explanatory diagram showing an example of a technique for obtaining grain boundaries from a subtracted image.
Fig. 11 is an explanatory diagram showing an example of the grain boundary image.
Fig. 12 is an explanatory diagram showing an example of the operation GUI of embodiment 3.
Description of the reference numerals
1 sample holder
2 electromagnetic coil
3 sample
4 sample normal direction
5 laser light
6 incident light
7 reflected light
8 detector
9 signal processing unit
10 storage part (database)
11 control device
12 image display terminal (GUI)
31 magnetization reversal region
41. 42 low field inversion region
43 magnetic field reversal region
44 non-inverting region
45 high magnetic field inversion region
61 area where scars are generated
62 non-flip area
71. 72, 73, 74, 75 windows
101. 111 particles
102. 112 grain boundary
121. 122, 123, 124, 125 windows
Detailed Description
The embodiments are described below using the drawings.
[ example 1 ]
The configuration of the image acquisition system of embodiment 1 will be described with reference to fig. 1.
The image acquisition system includes a stage mechanism system, an optical system, and an image processing system.
The sample stage mechanism system has: a sample holder (holder) 1 having a sample stage for holding a sample 3 of a magnetic material and movable in XYZ axes; and an electromagnetic coil 2 capable of applying an external magnetic field. The optical system has a detector 8. The image processing system has a control device 11 and an image display terminal (GUI) 12. The control device 11 includes a signal processing unit 9 and a storage unit (database) 10.
The laser light 5 is incident on the plane of the sample 3 as incident light 6, and reflected light 7 reflected on the plane of the sample 3 is detected by a detector 8. Here, 4 represents the sample normal direction. The detection signal detected by the detector 8 is sent to the signal processing unit 9, and is subjected to predetermined processing.
An image acquisition method of embodiment 1 will be described with reference to fig. 2.
First, the sample 3 is fixed to the sample holder 1, and the surface shape of the sample 3 mounted on the sample holder 1 is observed, thereby obtaining a shape image (S101). In addition, no external magnetic field is applied at this point in time. That is, an optical microscopic image is obtained without a magnetic field. The shape image can also be photographed using an optical microscope or the like.
Then, light of a predetermined intensity is irradiated to the same field of view, and a magnetic domain image of the sample 3 serving as a reference is acquired (S102). No external magnetic field is applied at this point in time either. That is, a magnetic domain image is acquired without a magnetic field.
The light used herein is visible light, ultraviolet light, or the like. The plane of the sample 3 of the magnetic material is made to be incident with light, and the polarization plane of the reflected light 7 is rotated, which is called Kerr effect. In a Kerr microscope, the orientation of magnetization of the sample 3 is detected using the Kerr effect, and a magnetic domain image is acquired. The longitudinal Kerr effect and the transverse Kerr effect are used when the magnetization of the sample 3 is oriented in the in-plane direction, and the polar Kerr effect is used when the magnetization of the sample 3 is oriented in the direction perpendicular to the sample plane to obtain a magnetic domain image.
In order to utilize the longitudinal Kerr effect and the transverse Kerr effect, the incident light 6 is obliquely incident from 45 degrees to the sample normal direction 4, and in order to utilize the polar Kerr effect, the incident light is incident from the sample normal direction 4 of the sample 3. Further, by shifting the polarizer of the Kerr microscope and the photodetector by about 3 to 5 degrees, a magnetic domain contrast is formed and a magnetic domain image can be obtained. Here, the magnetic domain image is acquired using a Kerr microscope, but other means may be used to acquire the magnetic domain image. Magnetic domain images may be acquired using, for example, a Magnetic Force Microscope (MFM), a Scanning Electron Microscope (SEM).
Next, a magnetic domain image is acquired in a state where an external magnetic field is applied by the electromagnetic coils 2 provided at both ends of the sample 3 (S103).
Next, a subtraction image is obtained in which a reference magnetic domain image is subtracted from a magnetic domain image obtained by applying an external magnetic field (S104). The region of domain inversion is extracted from the obtained subtracted image to determine a domain inversion region (S105).
By repeating the above steps (S101 to S105), a subtracted image in which the external magnetic field is changed is obtained, and a domain inversion region in which the domain is inverted is extracted from the subtracted image, and is collected into one image to be synthesized. Thus, a drawn image of the domain inversion region, that is, a composite image is obtained.
In this case, the region where the magnetization is not reversed is determined as a nonmagnetic region such as a grain boundary region, and a grain boundary image can be formed, so that the analysis of the grain size distribution is effective in the material analysis as in the case of the drawing image of the strain distribution. All the images acquired here are stored in a database as the storage unit 10.
Then, the strain amount of each magnetic domain inversion region is calculated (S106).
Next, in the drawn image (composite image), a strain distribution image is created and acquired by associating the magnetic domain inversion region and the strain amount (S107).
Finally, strain causes are investigated using the strain distribution image (S108).
A method of acquiring a subtracted image is described with reference to fig. 3.
(a) Is a magnetic domain image obtained by applying a predetermined external magnetic field. (b) Is a reference magnetic domain image before the magnetic field is applied (no magnetic field) in the same field of view. (c) is an image in which the image (b) is subtracted from the image (a). By applying a given external magnetic field, the contrast of the region where magnetization is inverted changes, and the magnetic domain inversion region 31 can be extracted.
Next, fig. 4 shows a subtraction image obtained by subtracting a reference magnetic domain image from a magnetic domain image obtained by applying an external magnetic field while changing the external magnetic field.
In the subtraction images of (a) and (b), low magnetic field inversion regions 41 and 42 are formed. In the subtraction image of (c), a medium magnetic field inversion region 43 and a non-inversion region 44 are formed. In the subtracted image of (c), a high magnetic field inversion region 45 is formed.
By repeating the above steps (S101 to SS 105), a magnetic domain image in which the contrast of each region varies according to each external magnetic field can be obtained.
Fig. 5 shows a drawing image (composite image) of the domain inversion region.
The subtraction images ((a) to (d)) obtained by subtracting the reference magnetic domain image from the magnetic domain image obtained by applying the external magnetic field while changing the external magnetic field shown in fig. 4 are synthesized to obtain a synthesized image having a plurality of magnetic domain inversion regions. In this way, in the composite image, the low magnetic field inversion regions 41, 42 inverted with the low magnetic field, the medium magnetic field inversion region 43 inverted with the medium magnetic field, the non-inversion region 44, and the high magnetic field inversion region 45 inverted with the high magnetic field are formed. By extracting the region where the magnetic domain is inverted, the images are collected and synthesized, and a drawing image of the inverted region can be obtained.
Next, as shown in fig. 6, strain distribution images are obtained by calculating the amounts of strain in each of the plurality of domain inversion regions and associating the domain inversion regions and the amounts of strain in the composite image.
Here, when the external magnetic field is Hinv, the anisotropy constant K at this time is set to be the anisotropy constant K u Characterized by the following equation 1.
K u ∝H inv x I s I s : spontaneous magnetization (math 1)
In addition, the stress σ is represented by the following equation 2 according to the equation of the magnetic anisotropy energy.
σ∝K u λ λ: magnetic strain constant (math figure 2)
Based on the expression 1, expression 2, and young' S modulus of each material, the strain epsilon is calculated in S106 of fig. 2.
Here, the strain amount epsilon=1.8x10 in the low magnetic field inversion regions 41, 42 -4 Strain amount epsilon=3.2x10 of middle magnetic field inversion region 43 -2 Strain amount epsilon=5.2x10 of high magnetic field inversion region 45 -2 . Here, 44 is a non-inverted region.
The obtained strain distribution image is stored in the storage unit 10. As shown in fig. 6, a strain distribution image can be obtained by associating the strain amount with the composite image of the inversion region.
The contents of the screen displayed on the image display terminal 12 will be described with reference to fig. 7. Fig. 7 is an example of an operation GUI. Here 71, 72, 73, 74, 75 are windows of the screen.
The shape image (shape image), the magnetic domain image (magnetic domain image), the subtraction image (subtraction image), and the strain distribution image (strain distribution image) stored in the storage unit 10 are collectively displayed on the screen of the image display terminal 12. In this way, the resulting images can all be displayed on the operation GUI. That is, the obtained strain distribution image and the shape image can be simultaneously displayed in the GUI. This makes it possible to easily establish correspondence with the surface structure, and to easily estimate and clarify the cause of the strain. As a result, the region 61 in fig. 6 can be determined as a flaw. The obtained subtraction image, strain distribution image, and shape image are all stored in the storage unit 10.
By using the screen of the image display terminal 12 for evaluation of a sample having magnetism, drawing of strain distribution of the sample and quantitative evaluation can be performed nondestructively. For this reason, it can also be used in quality control of samples.
[ example 2 ]
An image acquisition method of embodiment 2 will be described with reference to fig. 8.
The difference from the image acquisition method of embodiment 1 shown in fig. 2 is that S102 in fig. 2 is replaced with S802. That is, in S102 of fig. 2, a magnetic domain image to be used as a reference is acquired without applying an external magnetic field, whereas in S802 of fig. 8, an external magnetic field is applied to acquire a magnetic domain image to be used as a reference. Other steps (S101, S103, S104, S105, S106, S107) are the same as the image acquisition method of embodiment 1 shown in fig. 2, and therefore, the description thereof is omitted.
In the image acquisition method of example 2, as shown in fig. 8, in the magnetic domain image acquisition serving as a reference, a magnetic domain image is acquired in a certain desired magnetic field application state. For example, it is also effective to apply a high magnetic field of a level where magnetization is completely saturated and use an image in a single magnetic domain state as a reference image. After the acquisition, the image was captured repeatedly a plurality of times in the same manner as in example 1 to acquire a magnetic domain image. By this means, a strain distribution image is obtained, and the cause of the occurrence of strain can be easily estimated and clarified.
[ example 3 ]
An image acquisition method of embodiment 3 will be described with reference to fig. 9.
In example 3, a grain boundary image was obtained in the same manner as in example 2 shown in fig. 8 until halfway. That is, a magnetic domain image is acquired, and a subtraction image of an image to which a predetermined external magnetic field is applied is acquired, thereby acquiring an image of a grain boundary region.
First, the sample 3 is fixed to the sample holder 1, and the surface shape of the sample 3 mounted on the sample holder 1 is observed, whereby a shape image is obtained (S901). In addition, no external magnetic field is applied at this point in time. That is, light microscopic images are acquired without a magnetic field.
Then, in the same field of view, a magnetic domain image is acquired with the external magnetic field set as a reference (S902).
Next, a magnetic domain image is acquired in a state where an external magnetic field is applied by the electromagnetic coils 2 provided at both ends of the sample 3 (S903).
Finally, a subtraction image is obtained in which the reference magnetic domain image is subtracted from the magnetic domain image obtained by applying the external magnetic field (S904).
As shown in fig. 10, when the grain boundary portion contains a nonmagnetic material or a composition, a structure, or the like different from the inside of the particle, a difference occurs between the contrast in the particle inner region and the contrast in the grain boundary portion. Here, 101 is a particle, and 102 is a grain boundary.
This allows the grain boundary region as shown in fig. 11 to be extracted by subtracting the image. By performing a plurality of evaluations while shifting the observation positions one by one, the particle shape, particle diameter measurement, particle diameter distribution, and the like of a large area can be evaluated. Here, 111 is a particle, and 112 is a grain boundary.
By combining the obtained data such as particle shape, particle size measurement, particle size distribution, and the like with the strain distribution image obtained in example 1 or example 2, the cause of occurrence of strain can be easily estimated and clarified.
An example of an operation screen of the GUI in embodiment 3 is shown in fig. 12. Here, 121, 122, 123, 124, 125 are windows of the screen.
The obtained subtraction image (subtraction image), strain distribution image (strain distribution image), shape image (shape image) and grain boundary image (grain boundary image) can be displayed simultaneously on the GUI. By comparing the images, correspondence with the surface structure and the particle structure can be easily established. This makes it possible to easily estimate and clarify the cause of the strain.
The evaluation of the sample having magnetism was performed using the operation screen of the GUI. This allows the strain distribution of the sample to be plotted and quantitatively evaluated without damage. Therefore, the method can also be used for quality control of materials.
In the above-described embodiments, the strain amount of the magnetic domain is estimated by measuring the value of the external magnetic field with the magnetic domain contrast inverted from the magnetic domain observation, forming a strain distribution image in the observation region. Then, the strain amount (. Epsilon.) of the magnetic domain in the magnetic body is calculated to obtain a strain distribution image in the observation region. That is, the magnetic domain change corresponding to the external magnetic field is extracted from the device provided with the method capable of capturing the magnetic domain structure in the same field of view as the surface shape image, and the data of the magnetic domain inversion by the external magnetic field is analyzed. Thus, the strain amount is calculated, and a strain distribution image is formed, and the surface shape image is displayed.
According to the above embodiment, the strain amount of the magnetic domain in the magnetic body is estimated, and the strain distribution image in the observation region can be obtained. In addition to the light microscopy-based shape image in the same field of view, magnetization inversion and magnetic domain structure due to the application of a magnetic field can be observed at the same time. The sample state and the grain boundary position can be confirmed by the grain boundary image from the thus obtained magnetic domain image or the subtraction image. This makes it possible to clarify the cause of strain. In addition, the sample can be evaluated in a simple manner without contact and processing in the atmosphere.
Further, since observation in the dynamic mode can be performed, strain evaluation can be performed in the component operation mode. Further, since the grain boundary position can be determined from the obtained subtraction image, the particle size measurement and the particle size distribution evaluation can be performed.
As described above, according to the above embodiment, in the image acquisition system, strain distribution can be easily measured over a wide range.
Claims (13)
1. An image acquisition system having a signal processing unit for acquiring an image of a sample containing a magnetic substance, the image acquisition system comprising,
the signal processing section performs the following processing:
using a reference external magnetic field as a reference, irradiating light to obtain a reference magnetic domain image of the sample as a reference,
multiple magnetic domain images are acquired in a state where an external magnetic field is applied while being changed,
obtaining a plurality of subtracted images respectively subtracting the reference magnetic domain image from a plurality of the magnetic domain images,
extracting domain inversion regions of domain inversion from a plurality of the subtracted images respectively,
by combining a plurality of the subtracted images each having the magnetic domain inversion region, a combined image having a plurality of the magnetic domain inversion regions is obtained,
the signal processing section performs the following processing:
the strain amounts of a plurality of the magnetic domain inversion regions are calculated respectively,
in the composite image, a strain distribution image is obtained by associating the domain inversion region and the strain amount.
2. The image acquisition system according to claim 1, wherein,
the signal processing section performs the following processing:
extracting at least a 1 st magnetic domain switching region switched with a 1 st magnetic field, a 2 nd magnetic domain switching region switched with a 2 nd magnetic field higher than the 1 st magnetic field, and a 3 rd magnetic domain switching region switched with a 3 rd magnetic field higher than the 2 nd magnetic field as a plurality of the magnetic domain switching regions,
at least a 1 st strain amount, a 2 nd strain amount larger than the 1 st strain amount, and a 3 rd strain amount larger than the 2 nd strain amount are calculated as strain amounts of the plurality of the magnetic domain inversion regions,
the 1 st magnetic domain inversion region and the 1 st strain amount are associated,
the 2 nd magnetic domain inversion region and the 2 nd strain amount are associated,
and the 3 rd magnetic domain turnover area and the 3 rd strain amount are correspondingly established.
3. The image acquisition system according to claim 1, wherein,
the signal processing section performs the following processing:
the reference magnetic domain image is acquired in a non-magnetic field state in which an external magnetic field is not applied as the reference external magnetic field.
4. The image acquisition system according to claim 1, wherein,
the signal processing section performs the following processing:
in a given field of view, taking a shape image of the surface shape of the sample in the absence of a magnetic field,
in the given field of view, the reference magnetic domain image and a plurality of the magnetic domain images are acquired.
5. The image acquisition system according to claim 4, wherein,
the image acquisition system further includes:
a storage unit for storing predetermined information; and
an image display terminal for displaying a given image,
the storage portion stores the shape image, the magnetic domain image, the subtraction image and the strain distribution image,
the image display terminal displays the shape image, the magnetic domain image, the subtraction image, and the strain distribution image stored in the storage unit.
6. The image acquisition system according to claim 1, wherein,
the signal processing section performs the following processing:
the reference magnetic domain image is acquired by irradiating the light using any one of a Kerr microscope, a magnetic microscope, and a scanning electron microscope.
7. The image acquisition system according to claim 4, wherein,
the signal processing section performs the following processing:
an optical microscope is used to take the shape image.
8. The image acquisition system according to claim 1, wherein,
the image acquisition system further includes:
a sample holder having a sample stage for holding the sample and being movable; and
an electromagnetic coil capable of applying the external magnetic field.
9. The image acquisition system according to claim 1, wherein,
the image acquisition system further includes:
and an image display terminal for displaying at least the grain boundary image of the sample.
10. An image acquisition method for acquiring an image of a sample including a magnetic substance, the image acquisition method comprising:
obtaining a reference magnetic domain image of the sample serving as a reference by irradiating light using a reference external magnetic field serving as a reference;
acquiring a plurality of magnetic domain images while applying an external magnetic field while changing the external magnetic field;
obtaining a plurality of subtraction images respectively subtracting the reference magnetic domain image from the plurality of magnetic domain images;
extracting magnetic domain inversion regions of magnetic domain inversion from the plurality of subtracted images, respectively;
obtaining a composite image having a plurality of the magnetic domain inversion regions by compositing a plurality of the subtracted images each having the magnetic domain inversion region;
calculating strain amounts of a plurality of the magnetic domain inversion regions respectively; and
in the composite image, a strain distribution image is obtained by associating the domain inversion region and the strain amount.
11. The method for acquiring an image according to claim 10, wherein,
in the step of acquiring the reference magnetic domain image, the reference magnetic domain image is acquired in a non-magnetic field state in which an external magnetic field is not applied as the reference external magnetic field.
12. The method for acquiring an image according to claim 10, wherein,
the image acquisition method further includes the steps of:
storing a shape image of a surface shape of the sample, the magnetic domain image, the subtraction image, and the strain distribution image; and
and displaying the stored shape image, the magnetic domain image, the deduction image and the strain distribution image together.
13. The method for acquiring an image according to claim 10, wherein,
the image acquisition method further includes the steps of:
displaying at least a grain boundary image of the sample.
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